How do aliens communicate?

[Extroheal]

In Aliens, the queen inaudibly commanded her warriors to withdraw after Ripley threatened her eggs. In Alien Resurrection, Ripley said "I can hear them, they're so close" and "it's the queen, she's in pain". These imply that the aliens have a way of communicating inaudibly.

According to the old novels (I don't know which ones since I haven't read them), aliens communicate by telepathy. The novelization of Alien Resurrection also says they're telepathic.

The video game Aliens versus Predator 2 says they communicate by ultrasound. I heard somewhere that an old version of the Alien Resurrection script also suggested this.

The Alien Legacy website says this about the alien queen: "It is believed that she communicates her will through the secretion of pheromones or possibly by an empathic link."

I prefer the ultrasound theory. What do you guys think?

[FACEBOX]

Ya know. I think they use radiation. 
That would explain how they can "see" through walls/doors/etc, and are able to sense: the queen inside the host/pray/communicate...blah,blah,blah. 

[SiL]

Who says they can see through walls and doors?

I'm partial to the idea that they use various methods to see their surroundings. Like ultrasound and pheromones.

[FACEBOX]

Who says they can see through walls and doors?

How do they always know where people are?

Notice how the aliens try to burst trough the door to get to Ripley 8 in A.R.
And how the dog alien knew how to get to the monks even though they shut the doors.
Also, how they got Hudson through the floor. (also happened in AR)

No one "said" it, but that's what I derived from the movies. 

[SiL]

Notice how the aliens try to burst trough the door to get to Ripley 8 in A.R.

Yes, but they may just be curious.

And how the dog alien knew how to get to the monks even though they shut the doors.

How is that proof? It's chasing the prisoners in a straight line, the door closes ... suddenly it's going to think 'whoa, hey, guess they just disappeared'? No. It knows the door's not permanent, and it knows they're on the other side cos it just watched them do so.

Also, how they got Hudson through the floor. (also happened in AR)

Grating, in both cases.

[FACEBOX]

But what about when....
....when....
.......ahh hell, I'm out of ammo. 

[xeno_alpha_07]

Also, how they got Hudson through the floor...

What SiL said.  Plus they are intelligent.

[SM]

Sound predominantly.

With some body language when necessary.

[Weyland]

Ya know. I think they use radiation. 
That would explain how they can "see" through walls/doors/etc, and are able to sense: the queen inside the host/pray/communicate...blah,blah,blah. 

How do you know they see through doors? I don't remember that.

[SM]

I don't think they can see through doors personally.  They could simply hear someone in the next room and find the most convenient way in.  Ripley8 had no trouble hearing the Aliens in another part of the ship.

Using heightened senses of 'speech' (for wont of a better word) and hearing would seem for all intents and purposes to be telepathy.  Doesn't mean that's what it is.  Telepathy's a bit to 'magical' for Alien I reckon.  If that was the case why didn't the Queen in AvP simply think at Grid and co to come rescue her instead screaming her head off?

The RPG had a sweet concept for communicating in a vaccuum.  They can change the colours on their head (outside the visible spectrum) and communicate that way.

[Uncanny Antman]

I tend to go with the sound theory too.  (It's a sound theory.  [Drum roll])

Remember Ash's motion detector?  ("...micro changes in air density")
If the Aliens were that attuned, it could easily account for their seemingly extra-sensory perception.

Not too dissimilar to bats using echolocation.